Natural gas, in its original state as it emerges from the well, contains various impurities, particulates and entrained liquids, which must be removed before the gas can be used by consumers. Typically, after the well is drilled, natural gas may be extracted from the ground using a compressor. Generally, such wells produce gas at a relatively low pressure. In some cases, natural gas producers employ production equipment that includes a driver and compressor along with related support equipment. Gas from a number of wells may be collected in a main pipeline and transported to a gathering facility, where the gas is processed using, for example, filtration, separation, and solvent extraction to remove contaminants prior to sending the gas to downstream processing plants.
One problem with natural gas production is that contaminants entrained in gas as it flows from the well can degrade the processing equipment. Compressors may be shut down by excessively contaminated natural gas. For example, salt deposits in the gas can plate out on high-temperature machine parts leading to excessive downtime and maintenance costs. Coal particulates can coat the internal components of compressors and equipment engines leading to increased maintenance. Also liquid slugging can cause the shut down and increased maintenance of compressors and other equipment, such as gas dehydration units downstream.
Conventional filtration systems may use inertial impaction, in which the natural gas is routed through a series of barriers, wherein each barrier forces the natural gas to flow in a different direction. The impact between the barrier and the natural gas causes contaminants to settle out of the natural gas. At the same time, this method can have the effect of significantly reducing the flow of natural gas through the filtration system.
The problem of restricted natural gas flow out of filtration systems only worsens as the filter elements become loaded with contaminants. Besides being costly, for filtration systems that use three or four cartridge-type filter elements, replacements of the filter elements may involve substantial downtime, as, typically, each filter element has a separate access port. As such, the filtration system pressure vessel may have four separate access ports, all of which would have to be accessed to replace the filter elements.
To protect natural gas processing equipment, the gas is typically filtered as it flows from the well. Typically, conventional filtration systems use pressure vessels that house a plurality of cartridge-type, canister-type, or tubular type filter elements, which may include, for example, a number of layers of pleated filter media or spirally wound media, as in U.S. Pat. No. 5,827,430. These types of filter elements may be multi-stage filter elements with very high efficiency ratings. Such cartridge-type filter elements tend to be costly, and may also be bulky and difficult to handle. Moreover, these types of filter elements may be relatively small and require frequent replacement because the buildup of particulates and entrained liquids within the filter elements leads to clogging and potential failure of the filter. The need to replace filter elements on a frequent basis further increases the operational costs of the filtration system. Additionally, the high-efficiency filter elements may also restrict the flow of natural gas across the filter element, further reducing the flow out of the filtration system.
It would therefore be desirable to have a natural gas filtration system that utilizes filter elements that are less expensive than conventional filter elements used in conventional filtration systems. It would also be desirable to have a natural gas filtration system in which the less-expensive filter element does not significantly restrict the flow of natural gas, and could be easily installed and removed, thereby minimizing downtime for the filtration system. Embodiments of the invention provide such a filtration system and such a filter element.